The present invention involves a methods and an apparatus for the uniform continuous heating and cooling of materials through the use of indirect heat exchangers. The present invention has particular application in the field of heating and cooling of liquid or semi liquid food products that include solid particles. Examples of such food products include yogurt fruit, spaghetti sauce, and various fruit products such as jams. There is often a need to heat or cool these products for both safety and processing reasons. In many of these circumstances the solid particles are of a fragile nature. In the past the heating or cooling of these materials has been a problem because the solid particles have been bruised or damaged thereby reducing the quality and value of the final product.
Because of these concerns many food processors have had to rely upon batch processing in order to produce a high quality product. Batch processing has the inherent problem of being slow and representing a bottle neck in the processing chain. Moreover, in both the batch processing and continuous processing there was a problem of uniformly heating both the liquid portion of the material and the solid particles. Conventional agitation to equalize temperature face the risk of damaging the solid particles. Therefore, there is a need for a method and apparatus that can continuously and uniformly heat or cool liquid materials containing solid particles.